The purpose of this research is to determine whether the risk of transmitting Cytomegalovirus (CMV) infections to premature infants by means of blood transfusion can be decreased by the use of pre-screened donors who have been shown to have no measurable antibody to CMV by the indirect hemagglutination (IHA) technique. A simplified means of performing the IHA test will be explored. The incidence of transfusion-acquired infection in premature infants receiving blood from CMV antibody negative donors will be compared with the incidence in those receiving blood from random donors whose antibody status will be determined retrospectively. Infants acquiring CMV infection will be followed for symptoms complicating their underlying illness, particularly for evidence of pneumonia, hepatitis, marrow dysfunction and poor weight gain. Following discharge, household contacts of infected infants will be followed for serological evidence of transmission of CMV infection from the infants to susceptible contacts, particularly those in the childbearing age group.